Recently, an amount of data dealt by a computer system has been increasing explosively. Along with an increase of the data amount, it is necessary to purchase new volumes as needed and add the volumes to a storage apparatus. The storage apparatus manages a plurality of hard disk drives (HDDs) by means of a RAID (Redundant Arrays of Independent/Inexpensive Disks) system. Then, the storage apparatus logicalizes physical storage areas of the plurality of hard disk drives and provides them as logical volumes to a host computer. The host computer accesses the provided logical volumes and requests reading/writing of data.
There is a function called Thin Provisioning as one of methods for providing logical volumes to a host computer. The thin provisioning function is a function providing virtualized logical volumes which do not have physical storage areas (hereinafter referred to as virtual volumes), to the host computer, and dynamically allocating the storage areas to the virtual volumes as triggered by write access by the host computer to the virtual volumes. The above-described thin provisioning function has the advantage that the virtual volumes of a larger capacity than that of storage areas, which can be actually provided, can be provided to the host computer and an inexpensive computer system can be configured by reducing the physical storage capacity, which should be prepared in advance, in a storage apparatus.
Furthermore, a method for managing each storage area provided by each of a plurality of kinds of storage media with different performance, which are mounted in a storage apparatus, as a plurality of kinds of different storage tiereds is suggested as a data management method for the storage apparatus equipped with the above-described thin provisioning function. Also, a technique called dynamic tiered control to migrate data in a storage tiered according to access frequency from the host computer is suggested. For example, storage areas are allocated from a high-speed and high-performance storage tier to an area where data with high access frequency is stored; and storage areas are allocated from a low-speed and low-performance storage tier to an area of the virtual volumes where data with low access frequency is stored. Furthermore, Patent Literature 1 discloses a technique of sorting data according to performance requirements and allocating storage areas of a high-performance storage tier to an area where data of a high performance requirement is stored.
If the above-described dynamic tiered control technique is used, cost performance for the storage apparatus can be enhanced. Accordingly, data stored in normal logical volumes are often managed by migrating such data to a storage tiered. Therefore, a sizing tool for calculating the structure of an appropriate storage tiered in accordance with a performance request from a user is provided.